The present invention relates to an airbag apparatus that protects an occupant from an impact by deploying and inflating an airbag at a position close to the occupant seated in a vehicle seat when an impact due to, for example, a collision is applied to the vehicle.
An airbag apparatus is known to be effective for protecting an occupant from an impact when an impact due to, for example, a collision is applied to an automobile. Airbag apparatuses typically generate inflation gas from a gas generator and deploy and inflate an airbag with the inflation gas at a position close to an occupant to reduce an impact.
One form of the gas generator includes an elongated or cylindrical gas generator having a gas outlet at one end. In an airbag apparatus that uses such a gas generator, a part of the gas generator from a longitudinally middle portion to the gas outlet is inserted inside the airbag through insertion openings of the airbag and along the inner wall surface of the airbag (for example, see Japanese Laid-Open Patent Publication No. 2013-86731). In such an airbag apparatus, a part of the gas generator from the middle portion to the proximal end is located outside the airbag and close to the outer wall surface of the airbag.
Furthermore, the airbag apparatus disclosed in Japanese Laid-Open Patent Publication No. 2013-86731 includes the airbag formed by laying a first base fabric sheet having an insertion opening over a second base fabric sheet having an insertion opening. The insertion opening of the first base fabric sheet is elliptical and has a major axis extending in the longitudinal direction of the gas generator. The insertion opening of the second base fabric sheet is circular and has a diameter shorter than the major axis of the insertion opening of the first base fabric sheet. The insertion opening of the second base fabric sheet is located inward of the insertion opening of the first base fabric sheet and forward of the insertion direction of the gas generator.
With the above structure, part of the airbag where the insertion opening of the first base fabric sheet does not lie over the insertion opening of the second base fabric sheet forms a low rigidity portion, which includes only the second base fabric sheet. The low rigidity portion is softer than the surrounding portion having a double-layer structure. Thus, the low rigidity portion reduces impact load applied to the gas generator when the airbag is deployed and inflated. The low rigidity portion also permits the insertion section of the gas generator to be easily inserted into the airbag through the insertion openings.
Furthermore, in addition to the apparatus disclosed in Japanese Laid-Open Patent Publication No. 2013-86731, various airbag apparatuses have been proposed that include an airbag with the double-layer structure, which is formed by laying a first base fabric sheet having an insertion opening over a second base fabric sheet having an insertion opening, and is formed such that a gas generator is inserted in the airbag through the insertion openings. For example, airbag apparatuses disclosed in Japanese Laid-Open Patent Publications No. 2008-120290 and No. 2010-95216 include a slack or a slit at the portion surrounding the insertion opening of the second base fabric sheet. When the insertion opening of the second base fabric sheet is tensioned as the airbag is deployed and inflated, the slack or the slit restrains increase in the gap between the inner edge of the insertion opening and the gas generator and thus restrain leakage of the inflation gas through the insertion portion of the airbag for the gas generator.
All the airbag apparatuses disclosed in Japanese Laid-Open Patent Publications No. 2013-86731, No. 2008-120290, and No. 2010-95216 include a first base fabric sheet and a second base fabric sheet each having an insertion opening into which a gas generator is inserted. Thus, a measurable gap is formed between the gas generator and the inner edges of the insertion openings. Although the airbags of all the airbag apparatuses disclosed in the above publications employ a double-layer structure to restrain leakage of the inflation gas through the gap as compared to a case in which the double-layer structure is not employed, the leakage restraint effect is insufficient, and there is room for improvement.